The primary objective is to determine the safety of a single IV dose of ABX-IL8 in the treatment of patients with plaque psoriasis involving greater than 3% of the body surface area. This is a multicenter, randomized, placebo-controlled, dose rising clinical trial examining the safety of administering a single intravenous infusion of ABX-IL8 in patients with moderate to severe plaque psorasis. The next dose level will be based on accumulated safety information as defined in the protocol.